A secondary battery, for example, includes a laminated electrode body in which an electrode member and a separator are laminated, a lead portion attached to the electrode member, an electrolytic solution, and a battery can. Then, a strip-like laminated electrode body is stored in the battery can in a wound state. Specifically, in the laminated electrode body, for example, a strip-like positive electrode member in which a positive electrode active material layer is formed on a positive electrode current collector, and a strip-like negative electrode member in which a negative electrode active material layer is formed on a negative electrode current collector, are laminated through the separator. The lead portion includes a positive electrode lead portion attached to the positive electrode current collector and a negative electrode lead portion attached to the negative electrode current collector. In general, the thickness of the lead portion is greater than the thickness of the positive electrode active material layer or the negative electrode active material layer. Accordingly, convexities and concavities are generated in a portion of the laminated electrode body in which the lead portion is disposed. In addition, a configuration or a structure of an end portion of the laminated electrode body is frequently different from that of a portion of the laminated electrode body other than the end portion, and thus, convexities and concavities are generated even in the end portion of the laminated electrode body. Furthermore, the portion of the laminated electrode body will be referred to as an “uneven portion”. Then, the cohesion of the separator with respect to the electrode member in the uneven portion is frequently insufficient compared to the cohesion of the separator with respect to the electrode member in the portion other than the uneven portion.
In a case where a short circuit or the like occurs in an external circuit to which the secondary battery is connected, and a large current flows into the secondary battery, an internal temperature of the secondary battery increases. As a result thereof, the separator contracts, and the separator does not partially exist between the positive electrode member and the negative electrode member, and thus, there is a concern that a short circuit occurs between the positive electrode member and the negative electrode member.